/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Comparator;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * Implementation of {@code Multimap} whose keys and values are ordered by their
 * natural ordering or by supplied comparators. In all cases, this
 * implementation uses {@link Comparable#compareTo} or
 * {@link Comparator#compare} instead of {@link Object#equals} to determine
 * equivalence of instances.
 * 
 * <p>
 * <b>Warning:</b> The comparators or comparables used must be <i>consistent
 * with equals</i> as explained by the {@link Comparable} class specification.
 * Otherwise, the resulting multiset will violate the general contract of
 * {@link SetMultimap}, which it is specified in terms of {@link Object#equals}.
 * 
 * <p>
 * The collections returned by {@code keySet} and {@code asMap} iterate through
 * the keys according to the key comparator ordering or the natural ordering of
 * the keys. Similarly, {@code get}, {@code removeAll}, and
 * {@code replaceValues} return collections that iterate through the values
 * according to the value comparator ordering or the natural ordering of the
 * values. The collections generated by {@code entries}, {@code keys}, and
 * {@code values} iterate across the keys according to the above key ordering,
 * and for each key they iterate across the values according to the value
 * ordering.
 * 
 * <p>
 * The multimap does not store duplicate key-value pairs. Adding a new key-value
 * pair equal to an existing key-value pair has no effect.
 * 
 * <p>
 * Depending on the comparators, null keys and values may or may not be
 * supported. The natural ordering does not support nulls. All optional multimap
 * methods are supported, and all returned views are modifiable.
 * 
 * <p>
 * This class is not threadsafe when any concurrent operations update the
 * multimap. Concurrent read operations will work correctly. To allow concurrent
 * update operations, wrap your multimap with a call to
 * {@link Multimaps#synchronizedSortedSetMultimap}.
 * 
 * @author Jared Levy
 * @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
 */
@GwtCompatible(serializable = true)
@SuppressWarnings({ "rawtypes", "unchecked" })
public class TreeMultimap<K, V> extends AbstractSortedSetMultimap<K, V> {
    private transient Comparator<? super K> keyComparator;
    private transient Comparator<? super V> valueComparator;

    /**
     * Creates an empty {@code TreeMultimap} ordered by the natural ordering of
     * its keys and values.
     */
    // eclipse doesn't like the raw Comparable
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create() {
        return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural());
    }

    /**
     * Creates an empty {@code TreeMultimap} instance using explicit
     * comparators. Neither comparator may be null; use
     * {@link Ordering#natural()} to specify natural order.
     * 
     * @param keyComparator
     *            the comparator that determines the key ordering
     * @param valueComparator
     *            the comparator that determines the value ordering
     */
    public static <K, V> TreeMultimap<K, V> create(
            Comparator<? super K> keyComparator,
            Comparator<? super V> valueComparator) {
        return new TreeMultimap<K, V>(checkNotNull(keyComparator),
                checkNotNull(valueComparator));
    }

    /**
     * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its
     * keys and values, with the same mappings as the specified multimap.
     * 
     * @param multimap
     *            the multimap whose contents are copied to this multimap
     */
    // eclipse doesn't like the raw Comparable
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create(
            Multimap<? extends K, ? extends V> multimap) {
        return new TreeMultimap<K, V>(Ordering.natural(), Ordering.natural(),
                multimap);
    }

    // Used by the TreeMultimap serialization test.
    TreeMultimap() {
        this(null, null);
    }

    // Must be package-private so multimaps with null comparators can be
    // serialized (which can be created with Multimaps.newTreeMultimap()). Once
    // that method is removed, this constructor can be made private.
    TreeMultimap(@Nullable Comparator<? super K> keyComparator,
            @Nullable Comparator<? super V> valueComparator) {
        super((keyComparator == null) ? new TreeMap<K, Collection<V>>()
                : new TreeMap<K, Collection<V>>(keyComparator));
        this.keyComparator = keyComparator;
        this.valueComparator = valueComparator;
    }

    private TreeMultimap(Comparator<? super K> keyComparator,
            Comparator<? super V> valueComparator,
            Multimap<? extends K, ? extends V> multimap) {
        this(keyComparator, valueComparator);
        putAll(multimap);
    }

    /**
     * {@inheritDoc}
     * 
     * <p>
     * Creates an empty {@code TreeSet} for a collection of values for one key.
     * 
     * @return a new {@code TreeSet} containing a collection of values for one
     *         key
     */
    @Override
    SortedSet<V> createCollection() {
        return (valueComparator == null) ? new TreeSet<V>() : new TreeSet<V>(
                valueComparator);
    }

    /**
     * Returns the comparator that orders the multimap keys.
     */
    public Comparator<? super K> keyComparator() {
        return keyComparator;
    }

    public Comparator<? super V> valueComparator() {
        return valueComparator;
    }

    /**
     * {@inheritDoc}
     * 
     * <p>
     * Because a {@code TreeMultimap} has unique sorted keys, this method
     * returns a {@link SortedSet}, instead of the {@link Set} specified in the
     * {@link Multimap} interface.
     */
    @Override
    public SortedSet<K> keySet() {
        return (SortedSet<K>) super.keySet();
    }

    /**
     * {@inheritDoc}
     * 
     * <p>
     * Because a {@code TreeMultimap} has unique sorted keys, this method
     * returns a {@link SortedMap}, instead of the {@link java.util.Map}
     * specified in the {@link Multimap} interface.
     */
    @Override
    public SortedMap<K, Collection<V>> asMap() {
        return (SortedMap<K, Collection<V>>) super.asMap();
    }

    /**
     * @serialData key comparator, value comparator, number of distinct keys,
     *             and then for each distinct key: the key, number of values for
     *             that key, and key values
     */
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(keyComparator());
        stream.writeObject(valueComparator());
        Serialization.writeMultimap(this, stream);
    }

    // reading data stored by writeObject
    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        stream.defaultReadObject();
        keyComparator = (Comparator<? super K>) stream.readObject();
        valueComparator = (Comparator<? super V>) stream.readObject();
        setMap(new TreeMap<K, Collection<V>>(keyComparator));
        Serialization.populateMultimap(this, stream);
    }

    private static final long serialVersionUID = 0;
}
